Zoom lens system, interchangeable lens apparatus and camera system

ABSTRACT

A zoom lens system, in order from an object side to an image side, comprising a first lens unit having positive optical power, a second lens unit having positive optical power, a third lens unit having positive optical power, a fourth lens unit having negative optical power, and at least one subsequent lens unit; an interchangeable lens apparatus; and a camera system are provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on application No. 2010-160378 filed in Japan on Jul. 15, 2010 and application No. 2011-124618 filed in Japan on Jun. 2, 2011, the contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a zoom lens system, an interchangeable lens apparatus, and a camera system. In particular, the present invention relates to: a zoom lens system which is suitable as an imaging lens system in, so-called, an interchangeable-lens type digital camera system; and an interchangeable lens apparatus and a camera system each employing this zoom lens system.

2. Description of the Background Art

In recent years, interchangeable-lens type digital camera systems have been spreading rapidly. Such interchangeable-lens type digital camera systems (also referred to simply as “camera systems”, hereinafter) include: a camera body having an image sensor such as a CCD (Charge Coupled Device), a CMOS (Complementary Metal-Oxide Semiconductor) or the like; and an interchangeable lens apparatus having an imaging lens system for forming an optical image on a light receiving surface of the image sensor.

Such interchangeable-lens type digital camera systems are able to take a high-sensitive and high-quality image because an image sensor used in the interchangeable-lens type digital camera systems is larger than that equipped for a compact type digital camera. In addition, the interchangeable-lens type digital camera systems can realize: high-speed focusing and high-speed image processing after image taking; and easy replacement of an interchangeable lens apparatus in accordance with a desired scene. Furthermore, an interchangeable lens apparatus having a zoom lens system that forms an optical image with variable magnification is popular because it allows free change of focal length without the necessity of lens replacement. Accordingly, for some time, various kinds of zoom lens systems have been proposed, which can be utilized as an imaging lens system in the interchangeable-lens type digital camera systems, such as a zoom lens system disclosed in each of Japanese Laid-Open Patent Publications No. 2002-287029 and No. 2001-117006.

Although the interchangeable-lens type digital camera systems show the above-mentioned various kinds of merits, the size and the weight of such interchangeable-lens type digital camera systems are greater than those of a compact type digital camera. It is preferable that the size and the weight of the interchangeable-lens type digital camera systems are as small as possible for easy carrying around and handling. Accordingly, a most compact and lightweight possible zoom lens system with maintaining imaging performance is desired as a zoom lens system to be used in the interchangeable-lens type digital camera systems.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a compact and lightweight zoom lens system having excellent imaging performance, which can be suitably used in an interchangeable-lens type digital camera system. Another object of the present invention is to provide compact and lightweight interchangeable lens apparatus and camera system.

The novel concepts disclosed herein were achieved in order to solve the foregoing problems in the conventional art, and herein is disclosed:

a zoom lens system, in order from an object side to an image side, comprising:

a first lens unit having positive optical power;

a second lens unit having positive optical power;

a third lens unit having positive optical power;

a fourth lens unit having negative optical power; and

at least one subsequent lens unit.

The novel concepts disclosed herein were achieved in order to solve the foregoing problems in the conventional art, and herein is disclosed:

an interchangeable lens apparatus comprising:

a zoom lens system; and

a lens mount section which is connectable to a camera body including an image sensor for receiving an optical image formed by the zoom lens system and converting the optical image into an electric image signal; wherein

the zoom lens system, in order from an object side to an image side, comprises:

a first lens unit having positive optical power;

a second lens unit having positive optical power;

a third lens unit having positive optical power;

a fourth lens unit having negative optical power; and

at least one subsequent lens unit.

The novel concepts disclosed herein were achieved in order to solve the foregoing problems in the conventional art, and herein is disclosed:

a camera system comprising:

an interchangeable lens apparatus including a zoom lens system; and

a camera body which is detachably connected to the interchangeable lens apparatus via a camera mount section, and includes an image sensor for receiving an optical image formed by the zoom lens system and converting the optical image into an electric image signal; wherein

the zoom lens system, in order from an object side to an image side, comprises:

a first lens unit having positive optical power;

a second lens unit having positive optical power;

a third lens unit having positive optical power;

a fourth lens unit having negative optical power; and

at least one subsequent lens unit.

According to the present invention, it is possible to provide: a compact and lightweight zoom lens system having excellent imaging performance; and an interchangeable lens apparatus and a camera system each employing this zoom lens system.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other objects and features of this invention will become clear from the following description, taken in conjunction with the preferred embodiments with reference to the accompanied drawings in which:

FIG. 1 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 1 (Example 1);

FIG. 2 is a longitudinal aberration diagram of an infinity in-focus condition of a zoom lens system according to Example 1;

FIG. 3 is a lateral aberration diagram of a zoom lens system according to Example 1 at a telephoto limit in a basic state where image blur compensation is not performed and in an image blur compensation state;

FIG. 4 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 2 (Example 2);

FIG. 5 is a longitudinal aberration diagram showing an infinity in-focus condition of a zoom lens system according to Example 2;

FIG. 6 is a lateral aberration diagram of a zoom lens system according to Example 2 at a telephoto limit in a basic state where image blur compensation is not performed and in an image blur compensation state;

FIG. 7 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 3 (Example 3);

FIG. 8 is a longitudinal aberration diagram showing an infinity in-focus condition of a zoom lens system according to Example 3;

FIG. 9 is a lateral aberration diagram of a zoom lens system according to Example 3 at a telephoto limit in a basic state where image blur compensation is not performed and in an image blur compensation state;

FIG. 10 is a lens arrangement diagram showing an infinity in-focus condition of a zoom lens system according to Embodiment 4 (Example 4);

FIG. 11 is a longitudinal aberration diagram showing an infinity in-focus condition of a zoom lens system according to Example 4;

FIG. 12 is a lateral aberration diagram of a zoom lens system according to Example 4 at a telephoto limit in a basic state where image blur compensation is not performed and in an image blur compensation state; and

FIG. 13 is a schematic construction diagram of an interchangeable-lens type digital camera system according to Embodiment 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1, 4, 7, and 10 are lens arrangement diagrams of zoom lens systems according to Embodiments 1, 2, 3, and 4, respectively. Each FIG. shows a zoom lens system in an infinity in-focus condition.

In each FIG., part (a) shows a lens configuration at a wide-angle limit (in the minimum focal length condition: focal length f_(w)), part (b) shows a lens configuration at a middle position (in an intermediate focal length condition: focal length f_(M)=√(f_(W)*f_(T))), and part (c) shows a lens configuration at a telephoto limit (in the maximum focal length condition: focal length f_(T)). Further, in each FIG., each bent arrow located between part (a) and part (b) indicates a line obtained by connecting the positions of each lens unit respectively at a wide-angle limit, a middle position and a telephoto limit, in order from the top. In the part between the wide-angle limit and the middle position, and the part between the middle position and the telephoto limit, the positions are connected simply with a straight line, and hence this line does not indicate actual motion of each lens unit. Moreover, in each FIG., an arrow imparted to a lens unit indicates focusing from an infinity in-focus condition to a close-object in-focus condition. That is, the arrow indicates the moving direction at the time of focusing from an infinity in-focus condition to a close-object in-focus condition.

In each FIG., symbol (+) or (−) imparted to the symbol of each lens unit corresponds to the sign of the optical power of the lens unit. In each FIG., the straight line located on the most right-hand side indicates the position of the image surface S. Further, as shown in each FIG., an aperture diaphragm A is provided within a third lens unit G3.

Each of the zoom lens systems according to Embodiments 1 to 4, in order from the object side to the image side, comprises a first lens unit G1 having positive optical power, a second lens unit G2 having positive optical power, the third lens unit G3 having positive optical power, a fourth lens unit G4 having negative optical power, and a fifth lens unit G5 having positive optical power.

(Embodiment 1)

The first lens unit G1, in order from the object side to the image side, comprises: a planer-convex first lens element L1 with the convex surface facing the object side; a negative meniscus second lens element L2 with the convex surface facing the object side; and a positive meniscus third lens element L3 with the convex surface facing the object side. The second lens element L2 and the third lens element L3 are cemented with each other.

The second lens unit G2, in order from the object side to the image side, comprises: a negative meniscus fourth lens element L4 with the convex surface facing the object side; and a planer-convex fifth lens element L5 with the convex surface facing the object side. The fourth lens element L4 and the fifth lens element L5 are cemented with each other.

The third lens unit G3, in order from the object side to the image side, comprises: a bi-concave sixth lens element L6; a bi-convex seventh lens element L7; a bi-concave eighth lens element L8; an aperture diaphragm A; a bi-convex ninth lens element L9; a negative meniscus tenth lens element L10 with the convex surface facing the object side; and a bi-convex eleventh lens element L11. The seventh lens element L7 and the eighth lens element L8 are cemented with each other, and the tenth lens element L10 and the eleventh lens element L11 are cemented with each other.

The fourth lens unit G4, in order from the object side to the image side, comprises: a negative meniscus twelfth lens element L12 with the convex surface facing the object side; a positive meniscus thirteenth lens element L13 with the convex surface facing the image side; and a bi-concave fourteenth lens element L14. The thirteenth lens element L13 and the fourteenth lens element L14 are cemented with each other.

The fifth lens unit G5, in order from the object side to the image side, comprises: a bi-convex fifteenth lens element L15; a negative meniscus sixteenth lens element L16 with the convex surface facing the image side; and a bi-convex seventeenth lens element L17.

(Embodiment 2)

The first lens unit G1, in order from the object side to the image side, comprises: a planer-convex first lens element L1 with the convex surface facing the object side; a negative meniscus second lens element L2 with the convex surface facing the object side; and a positive meniscus third lens element L3 with the convex surface facing the object side. The second lens element L2 and the third lens element L3 are cemented with each other.

The second lens unit G2, in order from the object side to the image side, comprises: a negative meniscus fourth lens element L4 with the convex surface facing the object side; and a positive meniscus fifth lens element L5 with the convex surface facing the object side. The fourth lens element L4 and the fifth lens element L5 are cemented with each other.

The third lens unit G3, in order from the object side to the image side, comprises: a bi-concave sixth lens element L6; a bi-convex seventh lens element L7; a bi-concave eighth lens element L8; an aperture diaphragm A; a bi-convex ninth lens element L9; a negative meniscus tenth lens element L10 with the convex surface facing the object side; and a bi-convex eleventh lens element L11.

The fourth lens unit G4, in order from the object side to the image side, comprises: a negative meniscus twelfth lens element L12 with the convex surface facing the object side; a positive meniscus thirteenth lens element L13 with the convex surface facing the image side; and a bi-concave fourteenth lens element L14. The thirteenth lens element L13 and the fourteenth lens element L14 are cemented with each other.

The fifth lens unit G5, in order from the object side to the image side, comprises: a bi-convex fifteenth lens element L15; a negative meniscus sixteenth lens element L16 with the convex surface facing the image side; and a bi-convex seventeenth lens element L17.

(Embodiment 3)

The first lens unit G1, in order from the object side to the image side, comprises: a planer-convex first lens element L1 with the convex surface facing the object side; a negative meniscus second lens element L2 with the convex surface facing the object side; and a positive meniscus third lens element L3 with the convex surface facing the object side. The second lens element L2 and the third lens element L3 are cemented with each other.

The second lens unit G2, in order from the object side to the image side, comprises: a negative meniscus fourth lens element L4 with the convex surface facing the object side; and a positive meniscus fifth lens element L5 with the convex surface facing the object side. The fourth lens element L4 and the fifth lens element L5 are cemented with each other.

The third lens unit G3, in order from the object side to the image side, comprises: a bi-concave sixth lens element L6; a bi-convex seventh lens element L7; a bi-concave eighth lens element L8; an aperture diaphragm A; a bi-convex ninth lens element L9; a negative meniscus tenth lens element L10 with the convex surface facing the object side; and a bi-convex eleventh lens element L11. The seventh lens element L7 and the eighth lens element L8 are cemented with each other, and the tenth lens element L10 and the eleventh lens element L11 are cemented with each other.

The fourth lens unit G4, in order from the object side to the image side, comprises: a negative meniscus twelfth lens element L12 with the convex surface facing the object side; a positive meniscus thirteenth lens element L13 with the convex surface facing the image side; and a bi-concave fourteenth lens element L14. The thirteenth lens element L13 and the fourteenth lens element L14 are cemented with each other.

The fifth lens unit G5, in order from the object side to the image side, comprises: a bi-convex fifteenth lens element L15; a negative meniscus sixteenth lens element L16 with the convex surface facing the image side; and a bi-convex seventeenth lens element L17.

(Embodiment 4)

The first lens unit G1, in order from the object side to the image side, comprises: a bi-convex first lens element L1; a negative meniscus second lens element L2 with the convex surface facing the object side; and a positive meniscus third lens element L3 with the convex surface facing the object side. The second lens element L2 and the third lens element L3 are cemented with each other.

The second lens unit G2, in order from the object side to the image side, comprises: a negative meniscus fourth lens element L4 with the convex surface facing the object side; and a positive meniscus fifth lens element L5 with the convex surface facing the object side. The fourth lens element L4 and the fifth lens element L5 are cemented with each other.

The third lens unit G3, in order from the object side to the image side, comprises: a bi-concave sixth lens element L6; a negative meniscus seventh lens element L7 with the convex surface facing the object side; a positive meniscus eighth lens element L8 with the convex surface facing the object side; an aperture diaphragm A; a bi-convex ninth lens element L9; a negative meniscus tenth lens element L10 with the convex surface facing the object side; and a bi-convex eleventh lens element L11.

The fourth lens unit G4, in order from the object side to the image side, comprises: a negative meniscus twelfth lens element L12 with the convex surface facing the object side; a positive meniscus thirteenth lens element L13 with the convex surface facing the image side; and a bi-concave fourteenth lens element L14. The thirteenth lens element L13 and the fourteenth lens element L14 are cemented with each other.

The fifth lens unit G5, in order from the object side to the image side, comprises: a bi-convex fifteenth lens element L15; a negative meniscus sixteenth lens element L16 with the convex surface facing the image side; and a bi-convex seventeenth lens element L17.

In the zoom lens systems according to Embodiments 1 to 4, at the time of zooming from a wide-angle limit to a telephoto limit, each of the lens units moves to the object side along the optical axis so that the interval between the first lens unit G1 and the second lens unit G2 is longer at a telephoto limit than at a wide-angle limit, the interval between the second lens unit G2 and the third lens unit G3 is shorter at a telephoto limit than at a wide-angle limit, the interval between the third lens unit G3 and the fourth lens unit G4 is shorter at a telephoto limit than at a wide-angle limit, and the interval between the fourth lens unit G4 and the fifth lens unit G5 is shorter at a telephoto limit than at a wide-angle limit. The aperture diaphragm A moves together with the third lens unit G3 along the optical axis.

Like in the zoom lens system according to each of the embodiments, it is preferable that the first lens unit G1 moves along the optical axis at the time of zooming from a wide-angle limit to a telephoto limit. In a case that the first lens unit G1 is a movable unit, the height of a light beam to following lens units can be reduced. As a result, the following lens units can be downsized, and the size and the weight of a focusing lens unit in a zoom lens system which adopts an inner-focus method can be reduced. In addition, it is preferable that the third lens unit G3 moves along the optical axis at the time of zooming. In a case that the third lens unit G3 is a magnification-changeable unit, imaging performance can be improved with realizing a downsized zoom lens system.

In the zoom lens system according to each of the embodiments, the second lens unit G2 which is located on the object side relative to the aperture diaphragm A moves to the object side along the optical axis at the time of focusing from an infinity in-focus condition to a close-object in-focus condition. In the zoom lens system according to each of the embodiments, the weight of a focusing lens unit can be reduced because the second lens unit G2, that is, the focusing lens unit, is composed of two lens elements. In addition, it is preferable that the second lens unit G2 which is the focusing lens unit is solely composed of a cemented lens element. In this case, chromatic aberration at a telephoto limit during focusing can be suitably compensated.

In the zoom lens system according to each of the embodiments, the fourth lens unit G4 which is located on the image side relative to the aperture diaphragm A is moved in a direction perpendicular to the optical axis in order to optically compensate image blur caused by vibration of an optical system. Because a lens unit which is located on the image side relative to the aperture diaphragm A and has negative optical power is an image blur compensating lens unit, the lens diameter of the lens unit can be reduced. In addition, when at least one lens unit having positive optical power is arranged on the image side relative to the image blur compensating lens unit, excellent optical performance during image blur compensation can be maintained.

In the zoom lens system according to each of the embodiments, the third lens unit G3 is, in order from the object side to the image side, composed of a first sub lens unit having negative optical power and a second sub lens unit having positive optical power. Here, in a case that a lens unit is composed of a plurality of lens elements, the sub lens unit indicates any one lens element included in the lens unit or alternatively a combination of a plurality of adjacent lens elements among the plurality of lens elements included in the lens unit. The aperture diaphragm A is arranged adjacent to the first sub lens unit. Because the aperture diaphragm A is arranged adjacent to the first sub lens unit having negative optical power, the height of an axial light beam passing through the aperture diaphragm A can be reduced. As a result, the outer diameter of a lens barrel can be reduced.

In the zoom lens system according to each of the embodiments, because the fifth lens unit G5 located on the image side relative to the fourth lens unit G4 which is the image blur compensating lens unit is composed of at least three lens elements, excellent optical performance during image blur compensation can be maintained.

The following description is given for conditions preferred to be satisfied by a zoom lens system like the zoom lens systems according to Embodiments 1 to 4. Here, a plurality of preferable conditions are set forth for the zoom lens system according to each embodiment. A construction that satisfies all the plurality of conditions is most desirable for the zoom lens system. However, when an individual condition is satisfied, a zoom lens system having the corresponding effect is obtained.

For example, a zoom lens system like the zoom lens systems according to Embodiments 1 to 4, which comprises, in order from the object side to the image side, a first lens unit having positive optical power, a second lens unit having positive optical power, a third lens unit having positive optical power, a fourth lens unit having negative optical power, and at least one subsequent lens unit (this lens configuration is referred to as a basic configuration of the embodiments, hereinafter), preferably satisfies the following condition (1). 0.2<D _(12W) /f _(W)<0.5  (1)

where

D_(12W) is an axial interval between the first lens unit and the second lens unit at a wide-angle limit, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The condition (1) sets forth the overall lengths in an axial direction of the first lens unit and the second lens unit at a wide-angle limit. When the condition (1) is satisfied, the second lens unit can be downsized. As a result, in a case that focusing is performed with the second lens unit, increase in the weight of the second lens unit can be suppressed. When the value exceeds the upper limit of the condition (1), the overall length of zoom lens system tends to be increased, which results in a difficulty in downsizing the zoom lens system. On the other hand, when the value goes below the lower limit of the condition (1), the second lens unit tends to grow in size, which results in a difficulty in focusing with the second lens unit.

When at least one of the following conditions (1)′ and (1)″ is satisfied, the above-mentioned effect is achieved more successfully. 0.3<D _(12W) /f _(W)  (1)′ D _(12W) /f _(W)<0.4  (1)″

For example, a zoom lens system having the basic configuration like the zoom lens systems according to Embodiments 1 to 4 preferably satisfies the following condition (2). 1.0<f ₁ /f ₂<2.0  (2)

where

f₁ is a focal length of the first lens unit, and

f₂ is a focal length of the second lens unit.

The condition (2) sets forth the ratio of the focal length of the first lens unit to the focal length of the second lens unit. When the condition (2) is satisfied, the overall length of lens system can be reduced along with suitable compensation of spherical aberration and magnification chromatic aberration at a telephoto limit. When the value exceeds the upper limit of the condition (2), the optical power of the second lens unit is increased, which may result in a deterioration in spherical aberration and magnification chromatic aberration. On the other hand, when the value goes below the lower limit of the condition (2), the optical power of the second lens unit is decreased, which may result in an increase in the amount of movement of the second lens unit during focusing with itself. As a result, the overall length of lens system is increased, which results in a difficulty in downsizing the lens system.

When at least one of the following conditions (2)′ and (2)″ is satisfied, the above-mentioned effect is achieved more successfully. 1.2<f ₁ /f ₂  (2)′ f ₁ /f ₂<1.8  (2)″

For example, a zoom lens system having the basic configuration like the zoom lens systems according to Embodiments 1 to 4, in which the third lens unit comprises at least two sub lens units, preferably satisfies the following condition (3). 0.05<D ₃ /f _(W)<0.25  (3)

where

D₃ is an axial interval between a sub lens unit (G31) and a sub lens unit (G32) which is different from the sub lens unit (G31) and is arranged on the image side relative to the sub lens unit (G31), and

f_(W) is a focal length of the entire system at a wide-angle limit.

The condition (3) sets forth the interval of each of the sub lens units constituting the third lens unit. When the condition (3) is satisfied, an increase in the overall length of lens system can be suppressed along with suppression of deterioration in performance, which is caused by manufacturing errors due to the sub lens units. When the value exceeds the upper limit of the condition (3), the optical power of each of the two sub lens units is decreased, which may result in an increase in the overall length of lens system. On the other hand, when the value goes below the lower limit of the condition (3), the optical power of each of the two sub lens units is increased, which may result in deterioration in spherical aberration at a wide-angle limit. Also, it becomes difficult to suppress deterioration in performance, which is caused by manufacturing errors.

When at least one of the following conditions (3)′ and (3)″ is satisfied, the above-mentioned effect is achieved more successfully. 0.08<D ₃ /f _(W)  (3)′ D ₃ /f _(W)<0.23  (3)″

The individual lens units constituting the zoom lens system according to each of the embodiments may be each composed exclusively of refractive type lens elements that deflect incident light by refraction (that is, lens elements of a type in which deflection is achieved at the interface between media having different refractive indices). Alternatively the lens units may employ any one of: or a combination of at least two of: diffractive type lens elements that deflect incident light by diffraction; refractive-diffractive hybrid type lens elements that deflect incident light by a combination of diffraction and refraction; and gradient index type lens elements that deflect incident light by distribution of refractive index in the medium.

(Embodiment 5)

FIG. 13 is a schematic construction diagram of an interchangeable-lens type digital camera system according to Embodiment 5.

The interchangeable-lens type digital camera system (referred to simply as “camera system”, hereinafter) 100 according to Embodiment 5 includes a camera body 101, and an interchangeable lens apparatus 201 which is detachably connected to the camera body 101.

The camera body 101 includes: an image sensor 102 which receives an optical image formed by a zoom lens system 202 of the interchangeable lens apparatus 201, and converts the optical image into an electric image signal; a liquid crystal monitor 103 which displays the image signal obtained by the image sensor 102; and a camera mount section 104. On the other hand, the interchangeable lens apparatus 201 includes: a zoom lens system 202 according to any of the above-mentioned Embodiments 1 to 4; a lens barrel 203 which holds the zoom lens system 202; and a lens mount section 204 connected to the camera mount section 104 of the camera body 101. The camera mount section 104 and the lens mount section 204 are physically connected to each other. Moreover, the camera mount section 104 and the lens mount section 204 function as interfaces which allow the camera body 101 and the interchangeable lens apparatus 201 to exchange signals, by electrically connecting a controller (not shown) in the camera body 101 and a controller (not shown) in the interchangeable lens apparatus 201. In FIG. 13, the zoom lens system according to Embodiment 1 is employed as the zoom lens system 202.

In Embodiment 5, the zoom lens system 202 according to any of Embodiments 1 to 4 is employed. Accordingly, a compact interchangeable lens apparatus having excellent imaging performance can be realized at low cost. Moreover, size reduction and cost reduction of the entire camera system 100 according to Embodiment 5 can be achieved.

Numerical examples are described below in which the zoom lens systems according to the embodiments are implemented. As described below, Numerical Examples 1, 2, 3, and 4 correspond to Embodiments 1, 2, 3, and 4, respectively. Here, in the numerical examples, the units of length are all “mm”, while the units of view angle are all “∘”. Moreover, in the numerical examples, r is the radius of curvature, d is the axial distance, nd is the refractive index to the d-line, and vd is the Abbe number to the d-line.

FIGS. 2, 5, 8, and 11 are longitudinal aberration diagrams of an infinity in-focus condition of the zoom lens systems according to Numerical Examples 1, 2, 3, and 4, respectively.

In each longitudinal aberration diagram, part (a) shows the aberration at a wide-angle limit, part (b) shows the aberration at a middle position, and part (c) shows the aberration at a telephoto limit. Each longitudinal aberration diagram, in order from the left-hand side, shows the spherical aberration (SA (mm)), the astigmatism (AST (mm)) and the distortion (DIS (%)). In each spherical aberration diagram, the vertical axis indicates the F-number (in each FIG., indicated as F), and the solid line, the short dash line and the long dash line indicate the characteristics to the d-line, the F-line and the C-line, respectively. In each astigmatism diagram, the vertical axis indicates the image height (in each FIG., indicated as H), and the solid line and the dash line indicate the characteristics to the sagittal plane (in each FIG., indicated as “s”) and the meridional plane (in each FIG., indicated as “m”), respectively. In each distortion diagram, the vertical axis indicates the image height (in each FIG., indicated as H).

FIGS. 3, 6, 9, and 12 are lateral aberration diagrams of the zoom lens systems according to Numerical Examples 1, 2, 3, and 4, respectively, at a telephoto limit in a basic state where image blur compensation is not performed and in an image blur compensation state.

In each lateral aberration diagram, the aberration diagrams in the upper three parts correspond to a basic state where image blur compensation is not performed at a telephoto limit, while the aberration diagrams in the lower three parts correspond to an image blur compensation state where the entirety of the fourth lens unit G4 is moved by a predetermined amount in a direction perpendicular to the optical axis at a telephoto limit. Among the lateral aberration diagrams of a basic state, the upper part shows the lateral aberration at an image point of 70% of the maximum image height, the middle part shows the lateral aberration at the axial image point, and the lower part shows the lateral aberration at an image point of −70% of the maximum image height. Among the lateral aberration diagrams of an image blur compensation state, the upper part shows the lateral aberration at an image point of 70% of the maximum image height, the middle part shows the lateral aberration at the axial image point, and the lower part shows the lateral aberration at an image point of −70% of the maximum image height. In each lateral aberration diagram, the horizontal axis indicates the distance from the principal ray on the pupil surface, and the solid line, the short dash line and the long dash line indicate the characteristics to the d-line, the F-line and the C-line, respectively. In each lateral aberration diagram, the meridional plane is adopted as the plane containing the optical axis of the first lens unit G1.

In the zoom lens system according to each of the numerical examples, the amount of movement (Y_(T): mm) of the image blur compensating lens unit (the fourth lens unit G4) in a direction perpendicular to the optical axis in the image blur compensation state at a telephoto limit is as shown in Table 1. The image blur compensation angle is 0.3°. That is, the following amount of movement of the image blur compensating lens unit is equal to the amount of image decentering in a case that the optical axis of the zoom lens system inclines by 0.3°.

TABLE 1 (Amount of movement of image blur compensating lens unit) Numerical Amount of movement Example (Y_(T): mm) 1 0.454 2 0.471 3 0.492 4 0.417

As seen from the lateral aberration diagrams, satisfactory symmetry is obtained in the lateral aberration at the axial image point. Further, when the lateral aberration at the +70% image point and the lateral aberration at the −70% image point are compared with each other in the basic state, all have a small degree of curvature and almost the same inclination in the aberration curve. Thus, decentering coma aberration and decentering astigmatism are small. This indicates that sufficient imaging performance is obtained even in the image blur compensation state. Further, when the image blur compensation angle of a zoom lens system is the same, the amount of parallel translation required for image blur compensation decreases with decreasing focal length of the entire zoom lens system. Thus, at arbitrary zoom positions, sufficient image blur compensation can be performed for image blur compensation angles up to 0.3° without degrading the imaging characteristics.

NUMERICAL EXAMPLE 1

The zoom lens system of Numerical Example 1 corresponds to Embodiment 1 shown in FIG. 1. Table 2 shows the surface data of the zoom lens system of Numerical Example 1. Table 3 shows the various data. Table 4 shows the single lens data. Table 5 shows the zoom lens unit data. Table 6 shows the magnification of zoom lens unit.

TABLE 2 (Surface data) Surface number r d nd vd Object surface ∞  1 120.51440 4.10180 1.48749 70.4  2 ∞ 0.20010  3 85.63570 1.90070 1.68893 31.2  4 54.12160 6.40130 1.49700 81.6  5 300.49570 Variable  6 35.26850 0.90010 1.62004 36.3  7 21.47210 4.20330 1.48749 70.4  8 ∞ Variable  9 −78.36840 0.80070 1.77250 49.6 10 29.03300 1.31110 11 34.49490 2.30120 1.94595 18.0 12 −162.95940 0.80060 1.90366 31.3 13 30.04010 4.26350 14(Diaphragm) ∞ 17.19270 15 51.39220 2.50010 1.58913 61.3 16 −73.34390 0.15010 17 26.75080 0.80000 1.84666 23.8 18 14.98860 5.02380 1.58913 61.3 19 −87.43470 Variable 20 23.23170 0.80040 1.77250 49.6 21 13.10340 2.08040 22 −50.37300 2.05100 1.84666 23.8 23 −17.74240 0.80040 1.77250 49.6 24 32.73270 Variable 25 22.41450 5.10110 1.51680 64.2 26 −22.45190 3.69230 27 −18.20830 0.80070 1.91082 35.2 28 −312.61980 0.15000 29 43.52060 2.30080 1.84666 23.8 30 −637.06910 (BF) Image surface ∞

TABLE 3 (Various data) Zooming ratio 2.82617 Wide-angle Middle Telephoto limit position limit Focal length 102.7209 174.1910 290.3070 F-number 4.11397 4.86257 5.77082 View angle 5.9655 3.5449 2.1271 Image height 10.8150 10.8150 10.8150 Overall length 142.4843 171.6440 200.8351 of lens system BF 15.42012 27.89229 42.07583 d5 33.6396 57.5749 83.6685 d8 7.4452 7.4930 2.3486 d19 12.4788 6.1560 1.0408 d24 2.8724 1.8996 1.0732 Entrance pupil 115.4380 228.5110 418.3390 position Exit pupil −33.5913 −31.0628 −29.0520 position Front principal 2.8704 −111.9699 −476.2374 points position Back principal 39.7634 −2.5471 −89.4719 points position

TABLE 4 (Single lens data) Lens Initial surface Focal element number length 1 1 247.2143 2 3 −218.8586 3 4 131.6830 4 6 −90.7942 5 7 44.0463 6 9 −27.3348 7 11 30.2670 8 12 −28.0134 9 15 51.6771 10 17 −41.5582 11 18 22.1210 12 20 −40.2950 13 22 31.4438 14 23 −14.7920 15 25 22.5787 16 27 −21.2550 17 29 48.1902

TABLE 5 (Zoom lens unit data) Front Back Initial Overall principal principal Lens surface Focal length of points points unit No. length lens unit position position 1 1 143.13818 12.60390 −0.61627 3.73372 2 6 87.20136 5.10340 −0.29909 1.42586 3 9 25.73933 35.14380 26.82042 56.50803 4 20 −15.70240 5.73220 2.42875 4.15321 5 25 41.35217 12.04490 −3.41568 0.71736

TABLE 6 (Magnification of zoom lens unit) Lens Initial Wide-angle Middle Telephoto unit surface No. limit position limit 1 1 0.00000 0.00000 0.00000 2 6 0.46352 0.53109 0.63144 3 9 0.74438 0.89878 1.02826 4 20 5.88911 49.44138 −10.71862 5 25 0.35317 0.05157 −0.29143

NUMERICAL EXAMPLE 2

The zoom lens system of Numerical Example 2 corresponds to Embodiment 2 shown in FIG. 4. Table 7 shows the surface data of the zoom lens system of Numerical Example 2. Table 8 shows the various data. Table 9 shows the single lens data. Table 10 shows the zoom lens unit data. Table 11 shows the magnification of zoom lens unit.

TABLE 7 (Surface data) Surface number r d nd vd Object surface ∞  1 97.05580 5.00000 1.48749 70.4  2 ∞ 0.20000  3 76.84090 1.29390 1.64769 33.8  4 44.52250 7.00000 1.49700 81.6  5 191.99550 Variable  6 35.88470 0.80630 1.60342 38.0  7 19.66490 4.39830 1.51680 64.2  8 360.35180 Variable  9 −52.20330 0.87400 1.72000 42.0 10 19.13230 0.59280 11 34.02180 3.06390 1.92286 20.9 12 −28.06000 1.05320 13 −24.68450 0.90640 1.85030 32.2 14 32.75630 2.97660 15(Diaphragm) ∞ 9.26370 16 34.58260 4.43760 1.49700 81.6 17 −26.52920 0.20000 18 33.70020 0.80000 1.69895 30.0 19 15.11570 2.02160 20 17.44850 4.71320 1.49700 81.6 21 −47.61970 Variable 22 46.02400 0.80000 1.83400 37.3 23 17.14210 1.14100 24 −89.19140 3.65950 1.72825 28.3 25 −11.35880 0.80000 1.72916 54.7 26 50.64630 Variable 27 25.53040 4.69370 1.52250 62.2 28 −23.16730 3.46600 29 −19.41550 0.80000 1.91082 35.2 30 −227.34850 0.28470 31 47.93580 2.14230 1.64769 33.8 32 −270.25050 (BF) Image surface ∞

TABLE 8 (Various data) Zooming ratio 2.82516 Wide-angle Middle Telephoto limit position limit Focal length 103.0002 173.1283 290.9919 F-number 4.12486 5.20034 5.81740 View angle 5.9334 3.5209 2.1179 Image height 10.8150 10.8150 10.8150 Overall length 143.7377 165.2802 194.8266 of lens system BF 15.54331 22.02404 47.08364 d5 36.4375 62.0970 76.2917 d8 3.2004 5.5943 2.0764 d21 16.4677 7.1749 0.9856 d26 4.7001 1.0013 1.0006 Entrance pupil 113.9530 288.8296 412.1775 position Exit pupil −37.1387 −28.4718 −27.5954 position Front principal 15.5746 −131.6231 −430.7004 points position Back principal 40.7375 −7.8480 −96.1653 points position

TABLE 9 (Single lens data) Lens Initial surface Focal element number length 1 1 199.0931 2 3 −166.0520 3 4 114.8189 4 6 −73.4747 5 7 40.0715 6 9 −19.3466 7 11 17.0669 8 13 −16.4357 9 16 30.9529 10 18 −39.9231 11 20 26.3265 12 22 −33.1712 13 24 17.5264 14 25 −12.6553 15 27 24.0406 16 29 −23.3497 17 31 63.0273

TABLE 10 (Zoom lens unit data) Initial Overall Lens surface Focal length of Front principal Back principal unit No. length lens unit points position points position 1 1 131.26505 13.49390 −1.01364 3.62928 2 6 90.27217 5.20460 −0.64130 1.18286 3 9 30.52850 30.90300 26.90568 55.84654 4 22 −18.23918 6.40050 1.75242 4.10345 5 27 49.83397 11.38670 −4.07030 −0.32306

TABLE 11 (Magnification of zoom lens unit) Lens Initial Wide-angle Middle Telephoto unit surface No. limit position limit 1 1 0.00000 0.00000 0.00000 2 6 0.51327 0.60095 0.66366 3 9 0.75680 1.01659 1.09472 4 22 4.45804 6.68241 −16.97186 5 27 0.45312 0.32308 −0.17979

NUMERICAL EXAMPLE 3

The zoom lens system of Numerical Example 3 corresponds to Embodiment 3 shown in FIG. 7. Table 12 shows the surface data of the zoom lens system of Numerical Example 3. Table 13 shows the various data. Table 14 shows the single lens data. Table 15 shows the zoom lens unit data. Table 16 shows the magnification of zoom lens unit.

TABLE 12 (Surface data) Surface number r d nd vd Object surface ∞  1 97.58170 5.00000 1.48749 70.4  2 ∞ 0.20000  3 77.36560 1.29570 1.64769 33.8  4 44.98920 7.00000 1.49700 81.6  5 207.32320 Variable  6 37.01110 0.95340 1.60342 38.0  7 21.08970 4.11870 1.51680 64.2  8 434.38390 Variable  9 −62.26150 0.80000 1.72342 38.0 10 20.52470 0.33290 11 29.96210 2.35210 1.94595 18.0 12 −61.25090 0.83240 1.90366 31.3 13 27.22150 5.59040 14(Diaphragm) ∞ 13.07180  15 45.92420 3.68310 1.49700 81.6 16 −30.17770 0.23690 17 25.55670 0.87400 1.68893 31.2 18 13.24150 4.87430 1.49700 81.6 19 −131.01560 Variable 20 69.36360 1.01050 1.85135 40.1 21 17.62790 1.17140 22 −67.00390 3.18160 1.72825 28.3 23 −9.69230 0.80000 1.72916 54.7 24 56.87670 Variable 25 23.22840 5.46410 1.51680 64.2 26 −18.28000 2.81560 27 −15.76010 0.80000 1.91082 35.2 28 −58.95560 0.20000 29 69.09920 1.74090 1.72342 38.0 30 ∞ (BF) Image surface ∞

TABLE 13 (Various data) Zooming ratio 2.82887 Wide-angle Middle Telephoto limit position limit Focal length 103.0904 173.3112 291.6294 F-number 4.16474 5.20642 5.78377 View angle 5.9036 3.4958 2.1038 Image height 10.8150 10.8150 10.8150 Overall length 142.6299 165.8948 190.7839 of lens system BF 15.55002 19.28288 39.75324 d5 32.6900 64.4341 78.0946 d8 6.5587 5.4483 2.3482 d19 14.7843 7.3192 1.0306 d24 4.6471 1.0105 1.1575 Entrance pupil 120.1290 325.8056 481.0697 position Exit pupil −37.3488 −28.2418 −27.8499 position Front principal 22.3147 −132.9081 −485.3437 points position Back principal 39.5395 −7.4165 −100.8454 points position

TABLE 14 (Single lens data) Lens Initial surface Focal element number length 1 1 200.1719 2 3 −168.6346 3 4 113.9776 4 6 −83.1190 5 7 42.7456 6 9 −21.2516 7 11 21.5397 8 12 −20.7624 9 15 37.2403 10 17 −41.0755 11 18 24.4719 12 20 −28.0126 13 22 15.2041 14 23 −11.2998 15 25 20.7237 16 27 −23.8266 17 29 95.5178

TABLE 15 (Zoom lens unit data) Initial Overall Lens surface Focal length of Front principal Back principal unit No. length lens unit points position points position 1 1 129.10738 13.49570 −0.78408 3.84161 2 6 90.10947 5.07210 −0.57563 1.20455 3 9 25.96025 32.64790 25.35015 55.73092 4 20 −16.20447 6.16350 1.60407 3.84112 5 25 43.10103 11.02060 −3.34409 0.51736

TABLE 16 (Magnification of zoom lens unit) Lens Initial Wide-angle Middle Telephoto unit surface No. limit position limit 1 1 0.00000 0.00000 0.00000 2 6 0.50781 0.61844 0.68242 3 9 0.75171 1.01106 1.12816 4 20 5.28860 6.94947 −17.67296 5 25 0.39553 0.30892 −0.16602

NUMERICAL EXAMPLE 4

The zoom lens system of Numerical Example 4 corresponds to Embodiment 4 shown in FIG. 10. Table 17 shows the surface data of the zoom lens system of Numerical Example 4. Table 18 shows the various data. Table 19 shows the single lens data. Table 20 shows the zoom lens unit data. Table 21 shows the magnification of zoom lens unit.

TABLE 17 (Surface data) Surface number r d nd vd Object surface ∞  1 99.57310 5.00000 1.48749 70.4  2 −3147.66250 0.20000  3 72.16670 1.30240 1.64769 33.8  4 43.25590 7.00000 1.49700 81.6  5 159.98290 Variable  6 35.57140 0.80000 1.60323 42.5  7 18.93980 3.91130 1.51680 64.2  8 229.23560 Variable  9 −69.76930 0.80000 1.69680 55.5 10 18.09430 0.77690 11 39.98810 1.58620 1.78590 43.9 12 21.43280 0.94750 13 24.19070 3.00980 1.94595 18.0 14 48.98130 1.70330 15(Diaphragm) ∞ 9.58480 16 32.52270 5.36790 1.49700 81.6 17 −33.22870 0.20000 18 37.79920 0.80000 1.69895 30.0 19 16.06200 1.11780 20 17.74900 4.68960 1.49700 81.6 21 −48.61900 Variable 22 47.30340 0.80000 1.78590 43.9 23 16.98380 1.20240 24 −99.80740 2.55330 1.75520 27.5 25 −12.38640 0.80000 1.72916 54.7 26 33.76420 Variable 27 20.59410 4.73920 1.49700 81.6 28 −23.01700 3.93520 29 −17.07860 0.80000 1.91082 35.2 30 −69.57970 0.44740 31 50.23860 3.34040 1.67270 32.2 32 −672.92370 (BF) Image surface ∞

TABLE 18 (Various data) Zooming ratio 2.82492 Wide-angle Middle Telephoto limit position limit Focal length 102.9987 173.1272 290.9632 F-number 4.10049 5.20062 5.77047 View angle 5.9664 3.5578 2.1267 Image height 10.8150 10.8150 10.8150 Overall length 143.8041 167.6709 197.2574 of lens system BF 15.58902 28.12740 49.48389 d5 37.4204 57.8916 76.4256 d8 3.3295 5.5053 2.0158 d21 16.3267 7.7441 0.9466 d26 3.7231 0.9871 0.9701 Entrance pupil 112.2787 234.2787 388.4450 position Exit pupil −36.2151 −28.9197 −27.8160 position Front principal 10.4918 −118.0030 −415.8017 points position Back principal 40.8054 −5.4563 −93.7058 points position

TABLE 19 (Single lens data) Lens Initial surface Focal element number length 1 1 198.0935 2 3 −169.7127 3 4 116.9585 4 6 −68.3897 5 7 39.6974 6 9 −20.5431 7 11 −61.0701 8 13 47.7114 9 16 33.9918 10 18 −40.5750 11 20 26.7902 12 22 −34.1122 13 24 18.4930 14 25 −12.3378 15 27 22.6881 16 29 −25.0322 17 31 69.6232

TABLE 20 (Zoom lens unit data) Initial Overall Lens surface Focal length of Front principal Back principal unit No. length lens unit points position points position 1 1 131.31005 13.50240 −1.35259 3.33392 2 6 97.36815 4.71130 −0.89859 0.76560 3 9 32.58968 30.58380 26.33294 54.52650 4 22 −17.08612 5.35570 1.80470 3.68344 5 27 40.81610 13.26220 −3.40571 0.80121

TABLE 21 (Magnification of zoom lens unit) Lens Initial Wide-angle Middle Telephoto unit surface No. limit position limit 1 1 0.00000 0.00000 0.00000 2 6 0.53503 0.60284 0.68098 3 9 0.73640 0.91862 1.03929 4 22 6.36529 426.75313 −6.04824 5 27 0.31277 0.00558 −0.51766

The following Table 22 shows the corresponding values to the individual conditions in the zoom lens systems of each of Numerical Examples.

TABLE 22 (Values corresponding to conditions) Numerical Example Condition 1 2 3 4 (1) D_(12W)/f_(W) 0.33 0.35 0.32 0.36 (2) f₁/f₂ 1.64 1.45 1.43 1.35 (3) D₃/f_(W) 0.21 0.12 0.18 0.11

The zoom lens system according to the present invention is applicable to a digital still camera, a digital video camera, a camera for a mobile telephone, a camera for a PDA (Personal Digital Assistance), a surveillance camera in a surveillance system, a Web camera, a vehicle-mounted camera or the like. In particular, the zoom lens system according to the present invention is suitable for a photographing optical system where high image quality is required like in a digital still camera system or a digital video camera system.

Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be understood that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modification depart from the scope of the present invention, they should be construed as being included therein. 

What is claimed is:
 1. A zoom lens system, in order from an object side to an image side, comprising: a first lens unit having positive optical power; a second lens unit having positive optical power; a third lens unit having positive optical power; a fourth lens unit having negative optical power; and at least one subsequent lens unit.
 2. The zoom lens system as claimed in claim 1, wherein an aperture diaphragm is arranged in the third lens unit, and a lens unit located on the object side relative to the aperture diaphragm performs focusing from an infinity in-focus condition to a close-object in-focus condition.
 3. The zoom lens system as claimed in claim 1, wherein an aperture diaphragm is arranged in the third lens unit, and a lens unit located on the image side relative to the aperture diaphragm optically compensates image blur.
 4. The zoom lens system as claimed in claim 3, wherein a lens unit having negative optical power optically compensates image blur, and at least one lens unit having positive optical power is arranged on the image side relative to the lens unit having negative optical power.
 5. The zoom lens system as claimed in claim 1, wherein the following condition (1) is satisfied: 0.2<D _(12W) /f _(W)<0.5  (1) where D_(12W) is an axial interval between the first lens unit and the second lens unit at a wide-angle limit, and f_(W) is a focal length of the entire system at a wide-angle limit.
 6. The zoom lens system as claimed in claim 1, wherein the following condition (2) is satisfied: 1.0<f ₁ /f ₂<2.0  (2) where f₁ is a focal length of the first lens unit, and f₂ is a focal length of the second lens unit.
 7. The zoom lens system as claimed in claim 1, wherein the third lens unit comprises at least two sub lens units, and the following condition (3) is satisfied: 0.05<D ₃ /f _(W)<0.25  (3) where D₃ is an axial interval between a sub lens unit (G31) and a sub lens unit (G32) which is different from the sub lens unit (G31) and is arranged on the image side relative to the sub lens unit (G31), and f_(W) is a focal length of the entire system at a wide-angle limit.
 8. An interchangeable lens apparatus comprising: the zoom lens system as claimed in claim 1; and a lens mount section which is connectable to a camera body including an image sensor for receiving an optical image formed by the zoom lens system and converting the optical image into an electric image signal.
 9. A camera system comprising: an interchangeable lens apparatus including the zoom lens system as claimed in claim 1; and a camera body which is detachably connected to the interchangeable lens apparatus via a camera mount section, and includes an image sensor for receiving an optical image formed by the zoom lens system and converting the optical image into an electric image signal. 